Abstract: In order to prevent and control the deflagration hazard of magnesium powder in fuel-rich conditions, the explosion suppression test device was used to test the effect of solid inerting angets (Mg(OH)2, Ca(OH)2, Ca(HCO3)2) on the explosion characteristics of magnesium powder. The particle size and concentration were considered .The results show that in the range of 17~74 μm, the maximum explosion pressure increases with the decrease of particle size. The magnesium powder with 17 um diameter the best explosion concentration of 350 g/m3, the maximum explosion pressure of 0.716 MPa. The addition of Mg(OH)2, Ca(OH)2, and Ca(HCO3)2 inerting agents make the maximum explosion pressure and maximum pressure rise decrease, and the inerting mechanism of solid inerting agents on oxygen-enriched magnesium powder under oxygen-enriched conditions is revealed. Pressure and the maximum pressure rise rate decreased, and the inerting ratios of three inerting agents for effective inerting and complete inerting of magnesium powder were obtained, among which Mg(OH)2 inerting effect was the optimal, and the inerting ratios of reaching effective inerting and complete inerting were 170% and 220%, respectively. The inerting mechanisms of different inertants were revealed. Mg(OH)2 was inerted by the thermal decomposition to produce MgO isolation layer, which was adsorbed to the surface of magnesium particles to hinder oxygen contact. Ca(OH)2 was inerted only by thermal decomposition, and Ca(HCO3)2 was inerted by thermal decomposition to produce CO2 to enhance the inerting effect. The obtained conclusions provide an important reference for realizing the effective inerting of magnesium powder explosion under rich combustion conditions.